bugGNU Octave - Bugs: bug #39535, FaceAlpha property not working for...

 
 

bug #39535: FaceAlpha property not working for OpenGL backend

Submitted by:  Rik <rik5>
Submitted on:  Fri 19 Jul 2013 11:01:35 PM UTC  
 
Category: Plotting with OpenGLSeverity: 3 - Normal
Priority: 5 - NormalItem Group: Incorrect Result
Status: NoneAssigned to: None
Originator Name: Open/Closed: Open
Release: devOperating System: GNU/Linux

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Fri 19 Jul 2013 11:58:32 PM UTC, comment #2:

Rats! I had thought it might be something simple like not passing a parameter over to OpenGL. I see that it is definitely non-trivial. I'll leave the bug report open as a placeholder.

Rik <rik5>
Project Administrator
Fri 19 Jul 2013 11:29:19 PM UTC, comment #1:

Support for transparency is globally not implemented yet in the OpenGL renderer. Although, transparency effects are possible in OpenGL, it's not trivial and requires sorting primitives from back to front [1]. I had some implementation in JHandles, but I never ported it to octave, IIRC I found is sub-optimal.

This was a suggestion for a GSoC project, but it wasn't picked up.

[1] http://www.opengl.org/archives/resources/faq/technical/transparency.htm

Michael Goffioul <goffioul>
Project Member
Fri 19 Jul 2013 11:01:35 PM UTC, original submission:

The FaceAlpha property determines the transparency of a face. The FLTK backend, however, interprets everything that is not 1 (opaque) as 0 (transparent). The property works with gnuplot.

Example code:

This seems like it should be possible since OpenGL can handle all kinds of strange colors/alpha blends.

Rik <rik5>
Project Administrator

 

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